The cryogenic rectification of feed air to produce at least one of product oxygen and product nitrogen is a well established industrial process. The feed air is separated in a cryogenic air separation plant, such as a double column plant having a higher pressure column and a lower pressure column. Refrigeration for the system is generally provided by the turboexpansion of a process stream such as a cooled feed air stream. Turboexpansion is an energy intensive operation and therefore any improvement to the energy efficiency of the refrigeration generation operation of a cryogenic air separation system would be very desirable.
Accordingly, it is an object of this invention to provide a cryogenic air separation system which can generate refrigeration by feed air turboexpansion with lower unit power requirements than comparable conventional systems.